The present invention relates to digital engine analyzers incorporating display devices. The invention has particular application to the use of such analyzers for analysis of particular types of engines.
It is known to provide engine analyzers with display screens which may constitute digital oscilloscopes. It is also known to provide such display screens with multiple display traces (e.g., two), so that a number of waveforms can be simultaneously displayed. Such analyzers acquire analog waveforms from an associated engine by means of pickup leads and then digitize the waveforms for storage in memory and display on the screen.
Such analyzers typically have a plurality of signal pickup leads adapted to be connected to selected points on a multi-cylinder internal combustion engine for,acquiring input analog waveform signals therefrom. These leads commonly include primary and secondary pickup leads for, respectively, acquiring signals from the primary and secondary windings of an ignition coil. Conventional ignition systems have a single ignition coil and a distributor for routing the secondary voltage to multiple spark plugs. With a conventional ignition system two probes are commonly used to obtain and identify the signals for all cylinders: one probe to obtain a common primary or secondary signal and a second probe to obtain a reference signal from one of the spark plug wires. This reference or sync signal is typically acquired from the spark plug wire for the no. 1 cylinder in the firing order. Thus, this lead permits the analyzer to keep track of which cylinder is firing, once the firing order of the engine is known.
In direct ignition engines each cylinder is provided with its own ignition coil having primary and secondary windings. Thus, existing engine analyzers have not been usable with direct ignition engines, since they are provided with only one primary and one secondary pickup lead. In order to view simultaneously ignition signals for multiple cylinders of a direct ignition engine, a separate set of probes for each cylinder would be required and no such arrangement is available in current analyzers.
Copending U.S. application Ser. No. 08/630,382, filed Apr. 10, 1996 and entitled xe2x80x9cEngine Analyzer with Single-Lead Ignition Scopexe2x80x9d, now U.S. pat. No. 5,778,328, discloses a digital engine analyzer which permits an operator to view the secondary signal for a specific cylinder by the use of only a single secondary pickup lead. However, that system, which is provided in order to enable an operator to make a quick check of an engine ignition system, permits the user to view only waveforms from the single cylinder to which the pickup lead is currently connected.
It is a general object of the invention to provide an improved engine analyzer apparatus which avoids the disadvantages of prior such apparatuses while affording additional structural and operating advantages.
An important feature of the invention is the provision of an engine analyzer with a display screen which can acquire and simultaneously display ignition signals from all cylinders of an engine with a direct, coil-per-cylinder ignition system.
In connection with the foregoing feature, another feature of the invention is the provision of an engine analyzer of the type set forth, which permits acquisition of cylinder waveform signals with the use of a single pickup lead.
Still another feature of the invention is the provision of a method of analyzing the operation of a multi-cylinder internal combustion engine with a direct, coil-per-cylinder ignition system.
In connection with the foregoing feature, a further feature of the invention is the provision of a method of the type set forth, which permits simultaneous display of waveform data acquired asynchronously from several cylinders, wherein xe2x80x9casynchronously,xe2x80x9d as used herein, means acquiring the waveforms for different cylinders from different engine cycles.
Certain ones of these and other features of the invention may be attained by providing a computer routine for use in an analysis apparatus of the type for analyzing the operation of a multi-cylinder internal combustion engine having an ignition coil with primary and secondary windings, wherein the apparatus includes waveform acquisition circuitry including primary and secondary pickup leads for respectively acquiring primary and secondary analog input waveform signals from primary and secondary coil windings and generating waveform data representative of such analog waveform signals, a memory for storing the waveform data, a user input device for inputting cylinder identifications, a display device having a display screen for displaying the waveform data, and a control processor coupled to the waveform acquisition circuitry and the memory and the input device and the display device. The computer routine is executed by the processor to permit use of a single pickup lead of the apparatus for analyzing ignition waveforms of direct ignition engines wherein each cylinder has its own ignition coil, the computer routine comprising: (a) a first portion, for establishing in the memory, cylinder buffers respectively associated with the cylinders of the engine under test; (b) a second portion for storing waveform data acquired from a cylinder by the single pickup lead in the cylinder buffer associated with that cylinder; and (c) a third portion for displaying on the display screen waveform data from any cylinder buffers in which such data has been stored.
Other features of the invention may be attained by providing a method of analyzing the operation of a multi-cylinder, direct ignition, internal combustion engine wherein each cylinder has its own ignition coil with primary and secondary windings, the method comprising the steps of: asynchronously acquiring analog waveform signals from a winding of each coil using a single pickup lead sequentially connected to the coils one cylinder at a time, generating digital waveform data from the acquired analog waveform signals and storing the data so that the data for each cylinder can be distinguished from the data for other cylinders, and displaying waveform data for any cylinders for which such data has been stored.
The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.